ByKasie Hunt and Ken Thomas, The Associated PressMay 30, 2012

President Barack Obama on Wednesday congratulated Mitt Romney on securing the Republican presidential nomination, a gesture coupled with a new line of attack on the GOP challenger that portrays his economic record while governor of Massachusetts as a failure.

The president called Romney and told him "he looked forward to an important and healthy debate about America's future," Obama campaign spokesman Ben LaBolt said. Romney's campaign said the call was "brief and cordial." Both men wished each other's families well during the upcoming race.

Romney's primary win in Texas on Tuesday pushed him past the 1,144-delegate threshold he needed to claim the nomination.

Obama took the formal step of congratulating his opponent even as his team looked to shift to the Massachusetts story under Romney. In a five-page memorandum from senior Obama campaign adviser David Axelrod, the Obama camp cast Romney as poor steward of the Massachusetts economy during his 2003-2007 tenure as governor.

"When it comes to Mitt Romney and his economic philosophy the facts are clear — it didn't work then, and it won't work now," Axelrod wrote.

Romney's campaign, meanwhile, was bringing attention to failed stimulus projects under Obama and federal money given to green energy companies like Solyndra, a solar firm that received hundreds of millions of dollars from the government only to go bankrupt.

The competing attack-lines came as Romney pivoted from a long primary slog to the Republican nomination and a new summertime window to sway voters who have not yet fully tuned into the presidential campaign. Romney hopes to present himself as a worthy replacement for Obama who can help revitalize a slow-moving economy, the most important issue for voters.

The country is "just beginning a general election, we've gone through a primary ... not a lot of people focus time on the characteristics of a new candidate like myself, and people will get to know me better. My guess is they're going to get to know more about me than they'd like to by the time we're finished," Romney said in an interview on Fox News that aired Wednesday but was taped over the weekend.

For months, Obama and his allies have signaled plans to target Romney's Massachusetts record, with advisers noting that the state's economy lagged in job creation and saw an increase in debt while he was governor. The critique builds upon a line of attack this month of Romney's record at private equity firm Bain Capital, which Obama's team contends led to job losses and bankrupt companies even while Bain profited.

"Whether companies succeeded or failed, Romney Economics netted huge profits for him and his investors, but sometimes proved devastating for the middle-class workers whose jobs, benefits and pensions were put at risk," Axelrod wrote in the memo released Wednesday.

Axelrod sought to link Romney's Bain record with his Massachusetts experience by noting that Romney ran for governor on the basis of his private-sector background. "Under Gov. Romney, the Massachusetts economy was not at the top or even in the middle, but close to the bottom of all the states," he wrote.

Republicans contend that Obama's critique of the Bain record will backfire because it will give voters the impression that he is anti-business. The focus on Obama's green energy record, including Energy Department funding for companies like Solyndra, gives Romney a chance to rebut Bain because Republicans say Obama essentially played the role of venture capitalist by investing government money in green energy companies.

On Tuesday, Romney raised money in Las Vegas with Donald Trump, the real estate mogul who has stoked doubts about whether Obama was born in America. It was the start of a weeklong push to raise millions of dollars during a West Coast trip designed to help Romney bring in as much cash as possible ahead of a ramped-up campaign schedule later this summer.

The former Massachusetts governor was looking to take advantage of his official claiming of the nomination, a triumph of endurance for a candidate who came up short four years ago and had to fight hard this year as voters flirted with a carousel of GOP rivals. According to the Associated Press count, Romney surpassed the 1,144 delegates needed to win the nomination by winning 105 delegates in the Texas primary, pushing his total to 1,191 delegates.

Romney must now fire up conservatives who still doubt him while persuading swing voters that he can do a better job fixing the nation's struggling economy than Obama. In Obama, he faces a well-funded candidate with a proven campaign team in an election that will be heavily influenced by the economy.

Romney has scheduled fundraisers this week in wealthy California enclaves like Hillsborough, near San Francisco, and Beverly Hills. He has at least one major fundraising event every day for the rest of the week, as well as a series of smaller events.